Buy a tube from a reputable dealer that has been selected for superior noise and microphonic performance. Several current production variants are quite satisfactory. Be willing to pay a bit extra for a kick butt specimen.

Thanks for the swift and helpful thoughts. To refine the question, I should have offered more perspective. So... I'm in Ireland, so EU or UK sources easier for me.
My friend at hifitubes.nl has offered me a Tele NOS ECC83 for about 150 bucks. Also a Tele NOS ECC803S for 700, LOL. But the Mic cost me only about 350 so I am wondering if there would be a transformation sonically? There are various UK, Billington, Langrex, Watford, and the German TubeDoctor offering 'Premium' new stock. On my island, a Guitar shop is offering a JJ ECC83S for about 15 bucks.

Perhaps start with the JJ and see if it actually makes a difference, there is not much point to tube rolling expensive tubes if you can't discern any difference between what is in there now and a different tube.

__________________"To argue with a person who has renounced the use of reason is like administering medicine to the dead." - Thomas Paine

Since this sounds like a higher end product, lets start by telling us the brand of tube that it came with. Specially selected tubes may be marked with paint on the tip of the tube. Does it have anything like that? How about some pictures.

It is remarkably well built and Recordings done on my friend's Mark 2 version are really quite something. There are gushing reviews of these mics out there. It didn't easily make it into my studio, my other vocal mics are U67's. Not kidding. The mic rings like a bell when gently tapped, so I presume that is the stock valve. Again my friend confirms same thing. He is using a Billington Gold ECC83.
DD

Sorted. All this new flood of information arriving today from the friend. Seems the Billington Gold is a very good choice, and his Guitar Amp guy actually keeps stock of them, and is coming to Cork this week. 20 Euros. Billington are wholesalers..... So basically I am buying a not new specially non microphonic Chinese build, from a reputable dealer, tested and guaranteed. And I have heard it in action on vocals on an album I played on.
Thanks for you speedy and helpful inputs.
Best, DD